Development and characterization of a 99m Tc-labeled Neuropeptide Y short analog with potential application in breast cancer imaging

Neuropeptide Y Peptide Family and Cancer: Antitumor Therapeutic Strategies

Currently available data on the involvement of neuropeptide Y (NPY), peptide YY (PYY), and pancreatic polypeptide (PP) and their receptors (YRs) in cancer are updated. The structure and dynamics of YRs and their intracellular signaling pathways are also studied. The roles played by these peptides in 22 different cancer types are reviewed (e.g., breast cancer, colorectal cancer, Ewing sarcoma, liver cancer, melanoma, neuroblastoma, pancreatic cancer, pheochromocytoma, and prostate cancer). YRs could be used as cancer diagnostic markers and therapeutic targets. A high Y1R expression has been correlated with lymph node metastasis, advanced stages, and perineural invasion; an increased Y5R expression with survival and tumor growth; and a high serum NPY level with relapse, metastasis, and poor survival. YRs mediate tumor cell proliferation, migration, invasion, metastasis, and angiogenesis; YR antagonists block the previous actions and promote the death of cancer cells. NPY favors tumor cell growth, migration, and metastasis and promotes angiogenesis in some tumors (e.g., breast cancer, colorectal cancer, neuroblastoma, pancreatic cancer), whereas in others it exerts an antitumor effect (e.g., cholangiocarcinoma, Ewing sarcoma, liver cancer). PYY or its fragments block tumor cell growth, migration, and invasion in breast, colorectal, esophageal, liver, pancreatic, and prostate cancer. Current data show the peptidergic system's high potential for cancer diagnosis, treatment, and support using Y2R/Y5R antagonists and NPY or PYY agonists as promising antitumor therapeutic strategies. Some important research lines to be developed in the future will also be suggested.

Neuroepithelial Interactions in Cancer

Nerves not only regulate the homeostasis and energetic metabolism of normal epithelial cells but also are critical for cancer, as cancer recapitulates the biology of neural regulation of epithelial tissues. Cancer cells rarely develop in denervated organs, and denervation affects tumorigenesis, in vivo and in humans. Axonogenesis occurs to supply the new malignant epithelial growth with nerves. Neurogenesis happens later, first in ganglia around organs or the spinal column and subsequently through recruitment of neuroblasts from the central nervous system. The hallmark of this stage is regulation of homeostasis and energetic metabolism. Perineural invasion is the most efficient interaction between cancer cells and nerves. The hallmark of this stage is increased proliferation and decreased apoptosis. Finally, carcinoma cells transdifferentiate into a neuronal profile in search of neural independence. The latter is the last stage in neuroepithelial interactions. Treatments for cancer must address the biology of neural regulation of cancer.

Correlation Analysis of Ultrasound Elastography Score with Invasive Breast Cancer and Biological Prognostic Factors

Invasive breast cancer (IBC) is a kind of malignant tumor in which cancer cells have broken through the basement membrane of breast ducts or lobular acini and invaded the stroma. Although ultrasound elastography score (UES) has shown unique advantages in the diagnosis of IBC, its value in the prognosis is not clear. Here, we explored the correlation of UES with IBC and biological prognostic factors. The datum of 86 patients with suspected IBC from January 2018 to December 2021 was collected. UE was applied in the examination of all patients. The lesion tissue of the malignant group was punctured to detect and analyze the expression of biological prognostic factors, including estrogen receptor (E receptor), progesterone receptor (P receptor), and human epidermal growth factor 2 (HER factor 2) and Ki67. The differences in UES under different biological prognostic factors were compared. The receiver operating characteristic (ROC) curve was applied to analyze the diagnostic value of UES of IBC and the expression of biological prognostic factors. Based on the pathological diagnosis results, the sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of UES in the diagnosis of IBC were analyzed. The correlation of UES with IBC and biological prognostic factors was analyzed by multiple linear regression and Spearman method. ROC analysis showed that the area under the curve of UES for diagnosing IBC and evaluating the expression of P receptor, HER factor 2, and Ki67 were 0.877, 0.704, 0.763, and 0.820, respectively (P＜0.05). The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of UES when diagnosing IBC were 92.42%, 90.00%, 91.86%, 96.83%, and 78.26%, respectively. The UES of E receptor expression (positive and negative group) showed no obvious variance ( $P$  > 0.05). The UES of P receptors (positive and negative), HER factor 2 (positive and negative), and Ki67 (high and low expression) showed obvious differences ( $P$  < 0.05). Multiple linear regression and Spearman indicated UES was significantly correlated with the expression of P receptor, HER factor 2, and Ki67 (P＜0.05). UES has a certain diagnostic value for IBC and is significantly correlated to the expression of P receptor, HER factor 2, and Ki67, which is helpful for evaluating the prognosis of patients with IBC.

Development and characterization of two novel 68 Ga-labelled neuropeptide Y short analogues with potential application in breast cancer imaging

In vivo receptor targeting with radiolabelled peptide-based probes is an attractive approach for the development of novel radiotracers for molecular imaging. This work presents the development and characterization of two novel neuropeptide Y analogues labelled with a positron emitter 68 Ga, for potential use in breast cancer imaging. Both analogues share the same amino acid sequence and were derivatized with NOTA through either a lysine linker (L1) or an acetylated lysine (L2). In both cases, a single product with radiochemical purity higher than 95% was obtained. The two complexes were hydrophilic, showed remarkable in vitro stability, good cellular uptake, binding affinity in the nanomolar range and high cellular internalization rate. Biodistribution studies revealed low blood uptake and elimination through the urinary tract. The addition of an acetyl group in the spacer increased the lipophilicity of C2 and modified the reactivity of the ε-amino group of the lysine which resulted in lower protein binding and lower percentage of injected dose in bladder and urine. The tumour versus muscle ratio was (3.8 ± 0.4) for 68 Ga-L1 and (4.7 ± 0.4) for 68 Ga-L2. These results encourage performing further studies in order to complete the evaluation of both tracers as potential radiopharmaceutical for breast cancer imaging.

Identification of a Suitable Peptidic Molecular Platform for the Development of NPY(Y1 )R-Specific Imaging Agents

NPY(Y1 )R (neuropeptide Y receptor subtype 1) is an important target structure for tumor-specific imaging and therapy as this receptor subtype is overexpressed in very high density and incidence especially in human breast cancer. Targeting this receptor with radiolabeled truncated analogues of the endogenous ligand NPY (neuropeptide Y) has, however, not yet resulted in satisfactory imaging results when using positron emission tomography (PET). This can be attributed to the limited stability of these PET imaging agents caused by their fast proteolytic degradation. Although highly promising NPY analogues were developed, their stability has only been investigated in very few cases. In this systematical work, we comparatively determined the stability of the five most promising truncated analogues of NPY that were developed over the last years, showing the highest receptor affinities and subtype selectivities. The stability of the peptides was assessed in human serum as well as in a human liver microsomal stability assay; these gave complementary results, thus demonstrating the necessity to perform both assays and not just conventional serum stability testing. Of the tested peptides, only [Lys(lauroyl)27 ,Pro30 ,Lys(DOTA)31 ,Bip32 ,Leu34 ]NPY27-36 showed high stability against peptidase degradation; thus this is the best-suited truncated NPY analogue for the development of NPY(Y1 )R-specific imaging agents.